When you lose someone you love and you go through a range of emotions and feelings.
Sorry this is really brief but I don't know how to expand on it further - as you can probably tell i'm not very eloquent with words.

Having to leave your best friends or your girl/boyfriend to go to separate colleges or start a new job on opposite sides of the country so you don't know when (if ever) you'll see them again. Listen to "Crimson and clover" by Joan Jett or "A praise chorus" by Jimmy Eat World.